This invention relates to static mixing devices for mixing viscous liquids and, more particularly, to an improvement which makes such a device significantly easier to disassemble and clean.
Static mixing devices have been used in the past for mixing an epoxy resin with a catalyst or promoter for delivery to a spraying apparatus such as the one shown in U.S. Pat. No. 3,032,278, which is owned by the same corporate entity which owns the subject invention. The apparatus shown in that patent operates to chop particles such as glass fibers from the end of a fiber rope and simultaneously spray the particles and the mixed liquids in such a way that they will merge together. The fibers are thus coated with the epoxy resin which will adhere to a surface and form a protective coating.
An example of a prior art static mixing device over which the subject invention is an improvement is shown and described in U.S. Pat. No. 3,089,683, which is also owned by the same corporate entity which owns the subject invention, the subject matter of which is incorporated by reference herein as though totally set forth. The mixer shown in that patent includes an elongated body with upper and lower body portions. The two viscous liquids to be mixed are introduced under pressure into a chamber located in the lower body portion. An initial mixing means for initially combining the liquids is located in the chamber and is threadedly connected with the upper end of the lower body. The upper body is in turn threadedly connected with the mixer. A diffuser which operates to thoroughly mix the liquids by imparting a turbulent flow pattern to them is inserted through the upper end of a longitudinal bore in the upper body portion and abuts against a shoulder located in the lower portion of the bore. The diffuser is formed integral with an upper enlarged portion which is threadedly connected with the upper end of the upper body portion. A coupling is mounted in the bore of the enlarged portion so that a hose can be connected for transmitting the mixed liquids to a spraying apparatus such as the one mentioned above.
Although the mixer just described works well for its intended purpose and effectively mixes viscous liquids, problems have been encountered when the mixing device is allowed to sit for awhile before it is cleaned. The liquid inside will harden which makes disassembly extremely difficult. This is because the only way the diffuser can be removed from the longitudinal bore is by unscrewing the enlarged portion of the diffuser from the upper body, and when the liquid inside hardens considerable force is normally required to loosen the diffuser so that it can be unscrewed. The diffuser has been known to become twisted and distorted when portions have stubbornly refused to loosen. Even attempts to unscrew the lower body portion from the upper body portion and heat the hardened resin with a torch to loosen the diffuser have not always been successful with the diffuser itself being burned on occasion. Difficulties have also been encountered in cleaning the initial mixing means since an opening does not extend through its entire length.
Even an arrangement such as the one shown in U.S. Pat. No. 4,027,857 is not satisfactory where a diffuser is formed as a removable element in a cylindrical housing. This is because the upstream end of the diffuser is not shaped in a way where force can be applied if the diffuser is stuck in the housing. Further, the downstream end of the element is held in place by a nozzle which is connected to the housing through female threads in the downstream end of the housing. This type of connection has been found to cause disassembly problems when the liquid is allowed to harden since the threads are exposed directly to the liquid which can find its way between the threads and adhere the adjacent surfaces together.